Adducts based on cyclic compounds and the use thereof as tanning agents and curing agents

ABSTRACT

The invention relates to adducts that can be obtained by reacting carbonyl compounds of general formula (I) in which the variables are defined as follows: R 1  and R 2  are selected among hydrogen, C 1 -C 12  alkyl, C 3 -C 12  cycloalkyl, substituted or unsubstituted, C 7 -C 13  aralkyl, C 6 -C 14  aryl, substituted or unsubstituted, whereby R 1  and R 2  can be bounds to one another while forming a ring. These carbonyl compounds are reacted with cyclic compounds of general formula (II) in which the variables are defined as follows: X is selected among oxygen, sulfur and N—R 8 ; R 3  and R 8  are the same or different and are selected among hydrogen, C 1 -C 12  alkyl, C 3 -C 12  cycloalkyl, substituted or unsubstituted, C 7 -C 13  aralkyl, C 6 -C 14  aryl, substituted or unsubstituted, formyl, CO—C 1 -C 12  alkyl, CO—C 3 -C 12  cycloalkyl, substituted or unsubstituted, CO—C 7 -C 13  aralkyl, CO—C 6 -C 14  aryl, whereby in the event X═N—R 8 , R 3  and R 8  can be bound to one another while forming a ring; R 4 , R 5  and R 6  are the same or different and are selected among hydrogen, C 1 -C 12  alkyl, C 3 -C 12  cycloalkyl, substituted or unsubstituted, C 7 -C 13  aralkyl, C 6 -C 14  aryl, substituted or unsubstituted, whereby two adjacent radicals at time can be bound to one another while forming a ring; n represents a integer ranging from 1 to 4, and; R 7  is the same or different and is selected among hydrogen, C 1 -C 12  alkyl, C 3 -C 12  cycloalkyl, substituted or unsubstituted, C 7 -C 13  aralkyl, C 6 -C 14  aryl, substituted or unsubstituted, whereby two adjacent radicals R 7  at time can be bound to one another or R 6  or R 4  can be bound to adjacent R 7  while forming a ring.

The present invention relates to adducts obtainable by reacting carbonylcompounds of the formula I

where

-   -   R¹ and R² are selected from hydrogen, C₁-C₁₂-alkyl,        C₃-C₁₂-cycloalkyl, substituted or unsubstituted, C₇-C₁₃-aralkyl,        C₆-C₁₄-aryl, substituted or unsubstituted, it being possible for        R¹ and R² to be linked to one another with formation of a ring,

with cyclic compounds of the formula II

where

-   -   X is selected from oxygen, sulfur and N—R⁸,    -   R³ and R⁸ are identical or different and are selected from        hydrogen, C₁-C₁₂-alkyl, C₃-C₁₂-cycloalkyl, substituted or        unsubstituted, C₇-C₁₃-aralkyl, C₆-C₁₄-aryl, substituted or        unsubstituted, formyl, CO—C₁-C₁₂-alkyl, CO—C₃-C₁₂-cycloalkyl,        substituted or unsubstituted, CO—C₇-C₁₃-aralkyl, CO—C₆-C₁₄-aryl,        where X is N—R⁸, it being possible for R³ and R⁸ to be linked to        one another with formation of a ring;    -   R⁴, R⁵ and R⁶ are identical or different and are selected from        hydrogen, C₁-C₁₂-alkyl, C₃-C₁₂-cycloalkyl, substituted or        unsubstituted, C₇-C₁₃-aralkyl, C₆-C₁₄-aryl, substituted or        unsubstituted, it being possible in each case for two        neighboring radicals to be linked to one another with formation        of a ring;    -   n is an integer in the range from 1 to 4;    -   R⁷ are identical or different and are selected from hydrogen,        C₁-C₁₂-alkyl, C₃-C₁₂-cycloalkyl, substituted or unsubstituted,        C₇-C₁₃-aralkyl, C₆-C₁₄-aryl, substituted and unsubstituted, it        being possible for R⁷ to be linked to R⁶ or in each case two        neighboring radicals R⁷ to be linked to one another with        formation of a ring.

Chrome tanning has been an important chemical treatment in leatherproduction for more than 100 years, cf. for example Ullmann'sEncyclopedia of Industrial Chemistry, Volume A15, pages 259 to 282 andin particular page 268 et seq., 5th edition (1990), Verlag ChemieWeinheim. For ecological reasons, however, alternatives to chrometanning are being sought. In the conventional chrome tanning, chromiumsalts in an amount of from 1.5 to 8% by weight, based on the pelt weightof the leather, or even more are available. In general, a considerablepart of this is not bound and enters the wastewater. Although it ispossible to free the wastewater from considerable amounts of chromium bychemical treatment with, for example, lime and iron salts,chromium-containing sludges result and have to be disposed of on speciallandfills or worked up in an expensive procedure.

Moreover, for example, the splitting of the hides and the leveling ofthe leather gives rise to chromium-containing leather wastes which mayaccount for from about 8 to 15% by weight, based on the hide weight, andlikewise have to be disposed of in an expensive procedure.

There has been no lack of attempts to reduce the chromium pollution ofthe wastewaters, for example by recycling of the chrome tanning liquoror chromium recycling methods. However, these methods have as a wholebeen unsatisfactory and in particular are not capable of solving theproblem of chromium-containing leather wastes.

Furthermore, processes in which some or all of the chromium was replacedby organic tanning agents are known. The use of the syntans, i.e.sulfonated condensates of formaldehyde and phenol or sulfonatednaphthalene/formaldehyde condensates, may be mentioned. The use ofvegetable tanning agents may furthermore be mentioned. However, bothclasses of tanning agents result in a high COD of the wastewater and arealso unacceptable for environmental reasons. Moreover, it has been foundthat the lightfastness of the leather is often unsatisfactory whensulfonated phenol/formaldehyde condensates are used (Ullmann'sEncyclopedia of Industrial Chemistry, Volume A15, pages 259 to 282 andin particular page 270 et seq., 5th edition (1990), Verlag ChemieWeinheim).

Tanning with the use of aldehydes, in particular dialdehydes, forexample glutaraldehyde, is furthermore known, cf. for example H.Herfeld, Bibliothek des Leders, Volume III, page 191, Umschau VerlagFrankfurt/Main, 1984. However, a disadvantage is that, with smallamounts of glutaraldehyde, for example from 0.5 to 0.9% by weight (basedon the pelt weight), the shrinkage temperatures do not exceed 70° C. andthe semifinished products used can therefore be dried only to aninsufficient extent. During the shaving, gluing occurs on the flesh sideof the leather and adversely affects the quality of the leather.

When larger amounts of glutaraldehyde are used, work safety problems mayarise owing to the toxic properties of the glutaraldehyde. Moreover, itis observed that in general completely tanned leathers are obtained andthat subsequent variable processing, as is desired in many tanneries, isno longer possible.

It is known that glutaraldehyde can be used in partially or completelyacetalated form for tanning, for example as methylacetal (Ullmann'sEncyclopedia of Industrial Chemistry, Volume A15, page 259 to 282 and inparticular page 273 et seq., 5th edition (1990), Verlag ChemieWeinheim). However, the tanned semifinished products described generallyrapidly tend to yellow.

DE-C 38 11 267 discloses that acetalation of glutaraldehyde or otherdialdehydes which have 2 to 8 carbon atoms with short-chainalkylglycols, alkylpolyglycols, aliphatic alcohols, glycerol orsaccharides has advantageous effects. However, the vapor pressure ofdialdehydes, which readily reform from the very hydrolysis-sensitiveacetals, is still marked. Furthermore, the performance characteristicsof the leathers thus obtained can be further improved.

It is an object of the present invention to provide a novel process forthe pretanning, tanning and posttanning of animal hides, which processavoids the abovementioned disadvantages. In particular, it is an objectof the present invention to provide a tanning agent which avoids thedisadvantages described above.

We have found that this object is achieved by the adducts defined at theoutset. In formula I

-   -   R¹ and R² are identical or different and are selected from        hydrogen,    -   C₁-C₁₂-alkyl, such as methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl, sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl,        n-decyl and n-dodecyl; preferably C₁-C₆-alkyl, such as methyl,        ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,        tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,        1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl and sec-hexyl,        particularly preferably C₁-C₄-alkyl, such as methyl, ethyl,        n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and        tert-butyl, very particularly preferably methyl;    -   C₃-C₁₂-cycloalkyl, such as cyclopropyl, cyclobutyl, cyclopentyl,        cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl,        cycloundecyl and cyclododecyl; preferably cyclopentyl,        cyclohexyl and cycloheptyl;        -   examples of substituted cycloalkyl radicals are:            2-methylcyclopentyl, 3-methylcyclopentyl,            cis-2,4-dimethylcyclopentyl, trans-2,4-dimethylcyclopentyl            2,2,4,4-tetramethylcyclopentyl, 2-methylcyclohexyl,            3-methylcyclohexyl, 4-methylcyclohexyl,            cis-2,5-dimethylcyclohexyl, trans-2,5-dimethylcyclohexyl,            2,2,5,5-tetramethylcyclohexyl, 2-methoxycyclopentyl,            2-methoxycyclohexyl, 3-methoxycyclopentyl,            3-methoxycyclohexyl, 2-Chlorocyclopentyl,            3-chlorocyclopentyl, 2,4-dichlorocyclopentyl,            2,2,4,4-tetrachlorocyclopentyl, 2-chlorocyclohexyl,            3-chlorocyclohexyl, 4-chlorocyclohexyl,            2,5-dichlorocyclohexyl, 2,2,5,5-tetrachlorocyclohexyl,            2-thiomethylcyclopentyl, 2-thiomethylcyclohexyl,            3-thiomethylcyclopentyl, 3-thiomethylcyclohexyl and further            derivatives;    -   C₇-C₁₃-aralkyl, preferably C₇— to C₁₂-phenylalkyl, such as        benzyl, 1-phenethyl, 2-phenethyl, 1-phenypropyl, 2-phenylpropyl,        3-phenylpropyl, neophyl(1-methyl-1-phenylethyl), 1-phenylbutyl,        2-phenylbutyl, 3-phenylbutyl and 4-phenylbutyl, particularly        preferably benzyl,    -   C₆-C₁₄-aryl, for example phenyl, 1-naphthyl, 2-naphthyl,        1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl,        3-phenanthryl, 4-phenanthryl and 9-phenanthryl, preferably        phenyl, 1-naphthyl and 2-naphthyl, particularly preferably        phenyl, unsubstituted or substituted by one or more        -   C₁-C₁₂-alkyl groups, such as methyl, ethyl, n-propyl,            isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,            n-pentyl, isopentyl, sec-pentyl, neopentyl,            1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl, sec-hexyl,            n-heptyl, isoheptyl, n-octyl, n-nonyl, n-decyl and            n-dodecyl; preferably C₁-C₆-alkyl, such as methyl, ethyl,            n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,            tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,            1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl, sec-hexyl,            particularly preferably C₁-C₄-alkyl, such as methyl, ethyl,            n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and            tert-butyl;        -   halogens, such as fluorine, chlorine, bromine and iodine,            chlorine and bromine being preferred,        -   C₁-C₁₂-alkoxy groups, preferably C₁-C₆-alkoxy groups, such            as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy,            isobutoxy, sec-butoxy, tert-butoxy, n-pentyloxy,            isopentyloxy, n-hexyloxy and isohexyloxy, particularly            preferably methoxy, ethoxy, n-propoxy and n-butoxy.

In a particular embodiment, R¹ and R² are covalently bonded to oneanother with formation of a 4- to 13-membered ring. Thus, R¹ and R²together may be C₃-C₈-alkylene, unsubstituted or substituted by, forexample, together C₃-C₈-alkylene, unsubstituted or substituted by, forexample, C₁-C₁₂-alkyl or C₆-C₁₄-aryl. Examples are —(CH₂)₃—,—(CH₂)₂—CH(CH₃)—, —(CH₂)₂—CH(C₂H₅)—, —(CH₂)₂—CH(C₆H₅)—, —(CH₂)₄—,—(CH₂)₅—, —(CH₂)₆, —(CH₂)₇—, —CH(CH₃)—CH₂—CH₂—CH(CH₃)—,—CH(CH₃)—CH₂—CH₂—CH₂—CH(CH₃)—, preferably C₃-C₅-allkylene, for example—(CH₂)₃—, —(CH₂)₄—, —(CH₂)₅—.

-   -   R¹ and R² are very particularly preferably each methyl.

In cyclic compounds of the formula II

the variables are defined as follows.

-   -   X is selected from oxygen, sulfur and N—R⁸, oxygen being        preferred.    -   R³ and R⁸ are identical or different and are selected from        hydrogen,    -   C₁-C₁₂-alkyl, such as methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl, sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl,        n-decyl and n-dodecyl; preferably C₁-C₆-alkyl, such as methyl,        ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,        tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,        1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl, sec-hexyl,        particularly preferably C₁-C₄-alkyl, such as methyl, ethyl,        n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and        tert-butyl, very particularly preferably methyl;    -   C₃-C₁₂-cycloalkyl, such as cyclopropyl, cyclobutyl, cyclopentyl,        cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl,        cycloundecyl and cyclododecyl; preferably cyclopentyl,        cyclohexyl and cycloheptyl;        -   examples of substituted cycloalkyl groups are:            2-methylcyclopentyl, 3-methylcyclopentyl,            cis-2,4-dimethylcyclopentyl, trans-2,4-dimethylcyclopentyl,            2,2,4,4-tetramethylcyclopentyl, 2-methylcyclohexyl,            3-methylcyclohexyl, 4-methylcyclohexyl,            cis-2,5-dimethylcyclohexyl, trans-2,5-dimethylcyclohexyl,            2,2,5,5-tetramethylcyclohexyl, 2-methoxycyclopentyl,            2-methoxycyclohexyl, 3-methoxycyclopentyl,            3-methoxycyclohexyl, 2-chlorocyclopentyl,            3-chlorocyclopentyl, 2,4-dichlorocyclopentyl,            2,2,4,4-tetrachlorocyclopentyl, 2-chlorocyclohexyl,            3-chlorocyclohexyl, 4-chlorocyclohexyl,            2,5-dichlorocyclohexyl, 2,2,5,5-tetrachlorocyclohexyl,            2-thiomethylcyclopentyl, 2-thiomethylcyclohexyl,            3-thiomethylcyclopentyl, 3-thiomethylcyclohexyl;    -   C₇-C₁₃-aralkyl, preferably C₇— to C₁₂-phenylalkyl, such as        benzyl, 1-phenethyl, 2-phenethyl, 1-phenylpropyl,        2-phenylpropyl, 3-phenylpropyl, neophyl        (1-methyl-1-phenylethyl), 1-phenylbutyl, 2-phenylbutyl,        3-phenylbutyl and 4-phenylbutyl, particularly preferably benzyl,    -   C₆-C₁₄-aryl, for example phenyl, 1-naphthyl, 2-naphthyl,        1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl,        3-phenanthryl, 4-phenanthryl and 9-phenanthryl, preferably        phenyl, 1-naphthyl and 2-naphthyl, particularly preferably        phenyl, unsubstituted    -   or substituted C₆-C₁₄-aryl, for example phenyl, 1-naphthyl,        2-naphthyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl,        2-phenanthryl, 3-phenanthryl, 4-phenanthryl and 9-phenanthryl,        preferably phenyl, 1-naphthyl and 2-naphthyl, particularly        preferably phenyl, substituted by one or more        -   C₁-C₁₂-alkyl groups, such as methyl, ethyl, n-propyl,            isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,            n-pentyl, isopentyl, sec-pentyl, neopentyl,            1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl, sec-hexyl,            n-heptyl, isoheptyl, n-octyl, n-nonyl, n-decyl and            n-dodecyl; preferably C₁-C₆-alkyl, such as methyl, ethyl,            n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,            tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,            1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl, sec-hexyl,            particularly preferably C₁-C₄-alkyl, such as methyl, ethyl,            n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and            tert-butyl;        -   halogens, such as fluorine, chlorine, bromine and iodine,            chlorine and bromine being preferred,        -   C₁-C₁₂₋alkoxy groups, preferably C₁-C₆-alkoxy groups, such            as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy,            isobutoxy, sec-butoxy, tert-butoxy, n-pentyloxy,            isopentyloxy, n-hexyloxy and isohexyloxy, particularly            preferably methoxy, ethoxy, n-propoxy and n-butoxy;    -   formyl,    -   CO—C₁-C₁₂-alkyl, such as acetyl, propionyl, n-butyryl,        isobutyryl, sec-butyryl, tert-butyryl, n-valeroyl, isovaleroyl,        sec-valeroyl, n-capryl and n-dodecanoyl; preferably        CO—C₁-C₄-alkyl, such as acetyl, propionyl, n-butyryl,        isobutyryl, sec-butyryl and tert-butyryl, very particularly        preferably acetyl;    -   CO—C₃-C₁₂-cycloalkyl, such as cyclopropylcarbonyl,        cyclobutylcarbonyl, cyclopentylcarbonyl, cyclohexylcarbonyl,        cycloheptylcarbonyl, cyclooctylcarbonyl, cyclononylcarbonyl,        cyclodecylcarbonyl, cycloundecylcarbonyl and        cyclododecylcarbonyl; preferably cyclopentylcarbonyl,        cyclohexylcarbonyl and cycloheptylcarbonyl;        -   examples of substituted cycloalkyl groups are:            2-methylcyclopentylcarbonyl, 3-methylcyclopentylcarbonyl,            2-methylcyclohexylcarbonyl, 3-methylcyclohexylcarbonyl,            4-methylcyclohexylcarbonyl,            cis-2,5-dimethylcyclohexylcarbonyl,            trans-2,5-dimethylcyclohexylcarbonyl,            2-methoxycyclopentylcarbonyl, 2-methoxycyclohexylcarbonyl,            3-methoxycyclopentylcarbonyl, 3-methoxycyclohexylcarbonyl,            2-chlorocyclopentylcarbonyl, 3-chlorocyclopentylcarbonyl,            2,4-dichlorocyclopentylcarbonyl, 2-chlorocyclohexylcarbonyl,            3-chlorocyclohexylcarbonyl, 4-chlorocyclohexylcarbonyl,            2,5-dichlorocyclohexylcarbonyl,            2-thiomethylcyclopentylcarbonyl,            2-thiomethylcyclohexylcarbonyl,            3-thiomethyl-cyclopentylcarbonyl, 3-thiomethylcyclohexyl;    -   CO—C₇-C₁₃-aralkyl, preferably CO—C₇-C₁₂-phenylalkyl, such as        phenylacetyl and ω-phenylpropionyl, particularly preferably        phenylacetyl,    -   C₆-C₁₄-aryl, for example benzoyl, 1-naphthoyl, 2-naphthoyl,        1-anthroyl, 2-anthroyl, 9-anthroyl, 1-phenanthroyl,        2-phenanthroyl, 3-phenanthroyl, 4-phenanthroyl and        9-phenanthroyl, preferably benzoyl, 1-naphthoyl and 2-naphthoyl,        particularly preferably benzoyl.    -   R⁴, R⁵ and R⁶ are identical or different and are selected from        hydrogen,    -   C₁-C₁₂-alkyl, such as methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl, sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl,        n-decyl, and n-dodecyl; preferably C₁-C₆-alkyl, such as methyl,        ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,        tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,        1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl, sec-hexyl,        particularly preferably C₁-C₄-alkyl, such as methyl, ethyl,        n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and        tert-butyl, very particularly preferably methyl;    -   C₃-C₁₂-cycloalkyl, substituted or unsubstituted, such as        cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,        cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl and        cyclododecyl; preferably cyclopentyl, cyclohexyl and        cycloheptyl;        -   examples of substituted cycloalkyl groups are:            2-methylcyclopentyl, 3-methylcyclopentyl,            cis-2,4-dimethylcyclopentyl, trans-2,4-dimethylcyclopentyl            2,2,4,4-tetramethylcyclopentyl, 2-methylcyclohexyl,            3-methylcyclohexyl, 4-methylcyclohexyl,            cis-2,5-dimethylcyclohexyl, trans-2,5-dimethylcyclohexyl,            2,2,5,5-tetramethylcyclohexyl, 2-methoxycyclopentyl,            2-methoxycyclohexyl, 3-methoxycyclopentyl,            3-methoxycyclohexyl, 2-chlorocyclopentyl,            3-chlorocyclopentyl, 2,4-dichlorocyclopentyl,            2,2,4,4-tetrachlorocyclopentyl, 2-chlorocyclohexyl,            3-chlorocyclohexyl, 4-chlorocyclohexyl,            2,5-dichlorocyclohexyl, 2,2,5,5-tetrachlorocyclohexyl,            2-thiomethylcyclopentyl, 2-thiomethylcyclohexyl,            3-thiomethyl-cyclopentyl, 3-thiomethylcyclohexyl;    -   C₇-C₁₃-aralkyl, preferably C₇— to C₁₂-phenylalkyl, such as        benzyl, 1-phenethyl, 2-phenethyl, 1-phenylpropyl,        2-phenylpropyl, 3-phenylpropyl, neophyl        (1-methyl-1-phenylethyl), 1-phenylbutyl, 2-phenylbutyl,        3-phenylbutyl and 4-phenylbutyl, particularly preferably benzyl,    -   C₆-C₁₄-aryl, for example phenyl, 1-naphthyl, 2-naphthyl,        1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl,        3-phenanthryl, 4-phenanthryl and 9-phenanthryl, preferably        phenyl, 1-naphthyl and 2-naphthyl, particularly preferably        phenyl, unsubstituted or substituted    -   C₆-C₁₄-aryl, for example phenyl, 1-naphthyl, 2-naphthyl,        1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl,        3-phenanthryl, 4-phenanthryl and 9-phenanthryl, preferably        phenyl, 1-naphthyl and 2-naphthyl, particularly preferably        phenyl, unsubstituted or substituted by one or more        -   C₁-C₁₂-alkyl groups, such as methyl, ethyl, n-propyl,            isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,            n-pentyl, isopentyl, sec-pentyl, neopentyl,            1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl, sec-hexyl,            n-heptyl, isoheptyl, n-octyl, n-nonyl, n-decyl and            n-dodecyl; preferably C₁-C₆-alkyl , such as methyl, ethyl,            n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,            tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,            1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl, sec-hexyl,            particularly preferably C₁-C₄-alkyl, such as methyl, ethyl,            n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and            tert-butyl;        -   halogens, such as fluorine, chlorine, bromine and iodine,            chlorine and bromine being preferred,        -   C₁-C₁₂-alkoxy groups, preferably C₁-C₆-alkoxy groups, such            as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy,            isobutoxy, sec-butoxy, tert-butoxy, n-pentyloxy,            isopentyloxy, n-hexyloxy and isohexyloxy, particularly            preferably methoxy, ethoxy, n-propoxy and n-butoxy;    -   it being possible in each case for two neighboring radicals to        be linked to one another with formation of a ring. For example,        R⁴ and R⁵ together may be C₁-C₈-alkylene, unsubstituted or        substituted by, for example, C₁-C₁₂-alkyl or C₆-C₁₄-aryl.        Examples are: —CH₂—, —CH(CH₃)—, —(CH₂)₂—, —CH₂—CH(CH₃)—,        —CH₂—CH(C₂H₅)—, —(CH₂)₃—, —(CH₂)₂—CH(CH₃)—, —(CH₂)₂—CH(C₂H₅)—.        —(CH₂)₂—CH(C₆H₅)—, —(CH₂)₄—, —(CH₂)₅—, —(CH₂)₆—, —(CH₂)₇—,        —CH(CH₃)—CH₂—CH₂—CH(CH₃)—, —CH(CH₃)—CH₂—CH₂—CH₂—CH(CH₃)—,        preferably C₃-C₅-alkylene, for example —(CH₂)₃—, —(CH₂)₄—,        —(CH₂)₅—.    -   n is an integer in the range from 1 to 4, in particular 2 or 3;    -   R⁷ are identical or different and are selected from hydrogen,    -   C₁-C₁₂-alkyl, such as methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl, sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl,        n-decyl, and n-dodecyl; preferably C₁-C₆-alkyl, such as methyl,        ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,        tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,        1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl, sec-hexyl,        particularly preferably C₁-C₄-alkyl, such as methyl, ethyl,        n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and        tert-butyl, very particularly preferably methyl;    -   C₃-C₁₂-cycloalkyl, substituted or unsubstituted, such as        cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,        cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl and        cyclododecyl; preferably cyclopentyl, cyclohexyl and        cycloheptyl;        -   examples of substituted cycloalkyl groups are:            2-methylcyclopentyl, 3-methylcyclopentyl,            cis-2,4-dimethylcyclopentyl, trans-2,4-dimethylcyclopentyl            2,2,4,4-tetramethylcyclopentyl, 2-methylcyclohexyl,            3-methylcyclohexyl, 4-methylcyclohexyl,            cis-2,5-dimethylcyclohexyl, trans-2,5-dimethylcyclohexyl,            2,2,5,5-tetramethylcyclohexyl, 2-methoxycyclopentyl,            2-methoxycyclohexyl, 3-methoxycyclopentyl,            3-methoxycyclohexyl, 2-chlorocyclopentyl,            3-chlorocyclopentyl, 2,4-dichlorocyclopentyl,            2,2,4,4-tetrachlorocyclopentyl, 2-chlorocyclohexyl,            3-chlorocyclohexyl, 4-chlorocyclohexyl,            2,5-dichlorocyclohexyl, 2,2,5,5-tetrachlorocyclohexyl,            2-thiomethylcyclopentyl, 2-thiomethylcyclohexyl,            3-thiomethylcyclopentyl, 3-thiomethylcyclohexyl;    -   C₇-C₁₃-aralkyl, preferably C₇— to C₁₂-phenylalkyl, such as        benzyl, 1-phenethyl, 2-phenethyl, 1-phenylpropyl,        2-phenylpropyl, 3-phenylpropyl, neophyl(1-methyl-1-phenylethyl),        1-phenylbutyl, 2-phenylbutyl, 3-phenylbutyl and 4-phenylbutyl,        particularly preferably benzyl,    -   C₆-C₁₄-aryl, substituted or unsubstituted, substituted and        unsubstituted C₆-C₁₄-aryl radicals being defined as above.

In one embodiment of the present invention, R⁷ may be linked to R⁶ or R⁷to R⁴ or R⁷ to R³ or, where n is greater than 1, in each case twoneighboring radicals R⁷ may be linked to one another with formation of aring. Thus, R⁶ and R⁷ together may be, for example, C₁-C₈-alkylene,unsubstituted or substituted by C₁-C₁₂-alkyl or C₆-C₁₄-aryl. Examplesare: —CH₂—, —CH(CH₃)—, —(CH₂)₂—, —CH₂—CH(CH₃)—, —CH₂—CH(C₂H₅)—,—(CH₂)₃—, —(CH₂)₂—CH(CH₃)—, —(CH₂)₂—CH(C₂H₅)—, —(CH₂)₂—CH(C₆H₅)—,—(CH₂)₄—, —(CH₂)₅—, —(CH₂)₆—, —(CH₂)₇—, —CH(CH₃)—CH₂—CH₂—CH(CH₃)—,—CH(CH₃)—CH₂—CH₂—CH₂—CH(CH₃)—, preferably C₃-C₅-alkylene, for example—(CH₂)₃—, —(CH₂)₄—, —(CH₂)₅—.

-   -   R⁴ to R⁷ are each very particularly preferably methyl. A very        particularly preferably chosen compound of the formula II is        2-methoxy-2,3-dihydro-4H-pyran (formula II.1).

Very particularly preferred carbonyl compounds of the formula I aremethyl ethyl ketone, formaldehyde and in particular acetone.

The novel adducts may be present in monomeric or dimeric form. The noveladducts can, however, also be present in oligomeric or polymeric form.Usually, the novel adducts are present as a mixture of dimers, oligomersor polymers, it furthermore being possible for the mixture to comprisecompounds of the formula H—X—R³ as a result of the preparation.Moreover, the novel adducts may be present as a mixture with impuritiesarising from the storage, for example dehydration products, oxidationproducts, hydrolysis products, crosslinked products or products of oneor more retroaldol reactions.

The novel adducts can be prepared by reacting one or more carbonylcompounds of the formula I with one or more cyclic compounds of theformula II.

The present invention furthermore relates to a process for thepreparation of the novel adducts. The novel process starts from at leastone cyclic compound of the formula II and at least one carbonyl compoundof the formula I, which are reacted with one another.

In one embodiment of the novel process, at least one cyclic compound ofthe formula II is reacted with up to 1 000, preferably up to 500,particularly preferably up to 200, mol % of at least one carbonylcompound of the formula I.

The novel process is preferably carried out at from 0 to 120° C., inparticular from 20 to 85° C. The reaction can be carried out at anydesired pressures from 0.1 to 100 bar, preferably at atmosphericpressure. The reaction is advantageously effected in the presence of asolvent, for example water, toluene, petroleum ether or n-heptane, butthe addition of solvents is not necessary. Where the carbonyl compoundof the formula I is liquid under reaction conditions, the use ofsolvents is not necessary for carrying out the novel process.

Some or all of the water formed during the reaction can be distilledoff—together with H—X—R³ formed in the course of the reaction.

In one embodiment of the present invention, the novel process is carriedout at acidic pH, i.e. for example at a pH of from 0.5 to 6.8,preferably from 0.7 to 4. Preferably, one or more acidic catalysts areused for carrying out the novel process at acidic pH.

Suitable acidic catalysts are, for example, phosphoric acid, inparticular orthophosphoric acid, formic acid, acetic acid, acidic silicagels, acidic alumina, dilute sulfuric acid and sulfonic acids, forexample methanesulfonic acid or paratoluenesulfonic acid. If nonaqueoussolvents are employed, the use of P₂O₅ or a molecular sieve isconceivable. From 0.1 to 20% by weight, based on carbonyl compound I, ofcatalyst may be used.

From 10 minutes to 24 hours, preferably from one to three hours, areexpedient as a reaction time for the formation of the novel adducts.

After the reaction, it is possible to work up the reaction mixturesformed by the novel process. Thus, any solvents used can be removedcompletely or to a certain extent, for example by distillation, e.g.under reduced pressure. For example, any acidic catalysts used can beneutralized, for example with aqueous alkaline solution, such as sodiumhydroxide solution or potassium hydroxide solution. It is also possibleto separate off unconverted starting materials, e.g. excess carbonylcompound of the formula I. Particularly where the carbonyl compound ofthe formula I is readily volatile, for example acetone or methyl ethylketone, it is advantageous to separate off carbonyl compounds of theformula I by distillation.

In some cases, the formation of a multiphase mixture is observed whencarrying out the novel process. In said cases, it is possible to removethe respective aqueous phase by, for example, decanting or other methodsknown per se.

When the novel process is carried out under the conditions describedabove, byproducts and secondary products are usually formed as a resultof the preparation, for example by elimination of water (dehydration),incomplete reactions, oxidation or intramolecular crosslinking. Duringthe storage of the novel adducts, byproducts arising from the storagemay furthermore occur, for example by elimination of water(dehydration), oxidations or dimerization, oligomerization orpolymerization and by crosslinking.

It is possible to purify and to isolate the novel adducts.

The present invention furthermore relates to mixtures of the noveladducts with the byproducts described above and arising from thepreparation and/or arising from the storage.

The present invention furthermore relates to the use of the noveladducts or of the novel mixtures for the production of semifinishedproducts and of leather.

In one embodiment of the present invention, the novel adducts or thenovel mixtures are used in the pretanning, tanning or posttanning ofanimal hides.

The present invention furthermore relates to the use of the noveladducts and of the novel mixtures for the pretanning, tanning orposttanning of animal hides and a process for the pretanning, tanning orposttanning of animal hides using the novel adducts or the novelmixtures.

The novel process for the pretanning, tanning or posttanning of animalhides, also referred to below as novel tanning process, starts fromhides of animals, for example cattle, pigs, goats or deer, which havebeen pretreated by conventional methods. It is not important for thenovel tanning process whether the animals were killed, for example byslaughtering, or have died of natural causes. The conventional methodsfor the pretreatment include, for example, liming, deliming, bating andpickling and mechanical operations, for example for fleshing the hides.

The novel tanning process is usually carried out in the presence ofwater.

The novel tanning process is carried out, for example, by a procedure inwhich one or more novel adducts, if desired as a mixture with byproductsarising from the preparation and/or arising from the storage, are addedin one portion or in a plurality of portions immediately before orduring a tanning step. The novel tanning process is preferably carriedout at a pH of from 2.5 to 4, it frequently being observed that the pHincreases by about 0.3 to three units while the novel tanning process isbeing carried out. It is also possible to increase the pH by about 0.3to three units by adding basifying agents.

The novel tanning process is carried out in general at from 10 to 45°C., preferably from 20 to 30° C. A duration of from 10 minutes to 12hours has proven useful, preferably from one to 3 hours. The noveltanning process can be carried out in any desired vessel customary inthe tannery, for example by tumbling in barrels or in rotatable drumshaving internals.

In one variant of the novel tanning process, the novel adducts or thenovel mixtures are used together with one or more conventional tanningagents, for example with chrome tanning agents, mineral tanning agents,syntans, polymer tanning agents or vegetable tanning agents, asdescribed, for example, in Ullmann's Encyclopedia of IndustrialChemistry, Volume A15, pages 259 to 282 and in particular page 268 etseq., 5th edition (1990), Verlag Chemie Weinheim. The weight ratio ofnovel adduct or novel mixture to conventional tanning agent or to thesum of the conventional tanning agents is expediently from 0.01:1 to100:1, any impurities of the adducts which are present and arise fromthe preparation or arise from the storage being included. In anadvantageous variant of the novel process, only a few ppm of theconventional tanning agents are added to the novel adducts. However, itis particularly advantageous completely to dispense with the admixtureof conventional tanning agents.

In one variant of the novel tanning process, one or more adducts, ifdesired together with byproducts arising from the preparation and/orarising from the storage, are added in one portion or in a plurality ofportions before or during the pretanning, in a particular variant asearly as in the pickle.

In a further variant of the novel tanning process, one or more adductsor novel mixtures are added, if desired together with byproducts arisingfrom the preparation and/or arising from the storage, in one portion orin a plurality of portions before or during a posttanning step. Thisvariant is also referred to below as novel posttanning process. Thenovel posttanning process starts from pretanned hides. These are treatedwith the novel adducts.

The novel posttanning process can be carried out under otherwiseconventional conditions. Expediently, one or more, for example from 2 to6, action steps are chosen, and washing with water can be effectedbetween the action steps. The temperature during the individual actionsteps is in each case from 5 to 60° C., preferably from 20 to 45° C.Expediently, further compositions usually used during the posttanningare employed, for example fatliquoring agents, leather dyes oremulsifiers.

A further aspect of the present invention relates to tanning agentscomprising one or more novel adducts as active components.

A further aspect of the present invention relates to semifinishedproducts and leathers produced by the novel process. The novel leathershave an advantageous quality overall, for example smooth grains, morehomogeneous tanning over the cross section, improved tensile strengthand body and little tendency to discolor, in particular to yellow.

In a special embodiment of the novel tanning process, the novel adductsare used, if desired as mixtures with byproducts arising from thepreparation or arising from the storage, in the form of activeingredients in powder form. The novel process furthermore relates toactive ingredients in the form of powder, comprising from 10 to 100,preferably from 40 to 90, % by weight of one or more novel adducts, ifdesired as a mixture with byproducts arising from the preparation orarising from the storage, and from 0 to 90, preferably from 10 to 60, %by weight of one or more additives.

Suitable additives are as a rule solid particulate substances. They arepreferably chosen from starch, silica, for example in the form of silicagel, in particular in the form of spheroidal silica gels, sheetsilicates, alumina and mixed oxides of silicon and aluminum.

The novel active ingredients in the form of powder may consist of fineparticles having a mean particle diameter of from 100 nm to 0.1 mm. Theparticle diameters follow a particle diameter distribution which can benarrow or broad. Bimodal particle size distributions are alsoconceivable. The particles themselves may be irregular or of sphericalshape, spherical particle shapes being preferred. The novel activeingredients in the form of powder can be metered in the novel tanningprocess under particularly hygienic conditions.

The present invention furthermore relates to a process for thepreparation of the novel active ingredients in the form of a powder. Thenovel process starts from novel adducts which are present in solution,suspension or emulsion or in isolated form and which may comprisebyproducts arising from the preparation or arising from the storage.Particularly preferably, reaction solutions as obtained in the novelprocess in the case of the preparation of the novel adducts are used asstarting materials.

It has proven useful initially to concentrate the reaction solutions toa residual solvent content of 50% by weight or less.

If desired, one or more additives are furthermore introduced.

The remaining volatile components are then removed. The resultingliquid, solid or oily concentrated reaction solutions are preferablysprayed in a spray dryer, preferably in a spray tower. Spray dryers areknown to a person skilled in the art and are described, for example, inVauck/Müller, Grundoperationen chemischer Verfahrenstechnik, VCHWeinheim, 1988, 7th edition, pages 638-740 and pages 765-766, and in theliterature cited therein.

In a special embodiment of the novel tanning process, the novel adducts,if desired as mixtures with byproducts arising from the preparation orarising from the storage, are used in the form of suspensions, forexample as aqueous suspensions.

In one embodiment of the novel tanning process, one or more noveladducts, if desired as mixtures with byproducts arising from thepreparation or arising from the storage, are used in a form diluted withpolar solvents. For example, alcohols or aqueous alcohols are suitable.Examples of suitable alcohols are ethylene glycol, glycerol, diethyleneglycol, triethylene glycol and polyethylene glycol and mixtures of theabove alcohols. Suitable concentrations of the polar solvent or solventsare, for example, from 1 to 80% by weight. In a special embodiment ofthe novel tanning process, one or more novel adducts, if desired asmixtures with byproducts arising from the preparation or arising fromthe storage, are used in a form diluted with polar solvents, andfurthermore additives are admixed. Suitable additives are, for example,starch, silica, sheet silicates, alumina and mixed oxides of silicon andaluminum.

The present invention furthermore relates to mixtures of the noveladducts, if desired as mixtures with byproducts arising from thepreparation or arising from the storage, with polar solvents, forexample alcohols or aqueous alcohols.

A further aspect of the present invention relates to the use of thenovel adducts, if desired as mixtures with byproducts arising from thepreparation or arising from the storage, for preservation, andpreservatives comprising the novel adducts or the novel mixtures. Thenovel preservatives are suitable for preserving products, for examplecosmetic products, and surfaces.

The Invention is Explained by the Examples.

1. Preparation of the Novel Adducts 1.1 to 1.5

The molecular weight determinations were effected by gel permeationchromatography under the following conditions:

Stationary phase: hydroxyethyl methacrylate gel crosslinked withethylene glycol dimethacrylate, commercially available as: HEMA BIO fromPSS, Mainz, Germany, flow rate: 1.5 ml/min, concentration: 1% by weightin the mobile phase with internal standard,

mobile phase: THF 30% by weight, acetonitrile 10% by weight, 0.1 molaraqueous NaNO₃ solution 60% by weight, internal standard: 0.01% by weightof benzophenone; detection: UV/vis at 254 nm.

1.1. Preparation of Adduct 1.1

In a 1 liter three-necked flask having a condenser, stirrer andthermometer, 114 g of 2-methoxy-2,3-dihydro-4H-pyran (formula II.1; 1mol), 114 ml of water and 58 g of acetone (1 mol) and 24.6 g of an 85%by weight aqueous orthophosphoric acid were mixed and were refluxed for3 hours. The pH was 1.

311 g of an aqueous dispersion of adduct 1.1 were obtained in the formof a honey-colored product having a broad molar mass distribution(Q=4.7) and an M_(n) of 380 g.

1.2. Preparation of Adduct 1.2

In a 1 liter three-necked flask having a condenser, stirrer andthermometer, 128 g of 2-methoxy-2,3-dihydro-4H-pyran (formula II.1; 1,12 mol), 128 ml of water and 112 g of acetone (2 mol) were mixed with 21g of a 50% by weight sulfuric acid and were refluxed for 3 hours. The pHwas 0.9.

Thereafter, the condenser was replaced by a distillation bridge andaqueous acetone was distilled off over a period of 3 hours at 70-80° C.and 1 bar. The mixture was allowed to cool to room temperature and a pHof 5.2 was established with 25% by weight of aqueous sodium hydroxidesolution. Thereafter, the mixture was transferred to a separating funneland about 25 ml of an aqueous phase were separated off and discarded.317 g of adduct 1.2 were obtained in the form of an amber-colored oilyproduct having a broad molar mass distribution (Q=5.1) and an M_(n) of610 g.

1.3. Preparation of Adduct 1.3

In a 1 liter three-necked flask having a condenser, stirrer andthermometer, 141 g of 2-methoxy-2,3-dihydro-4H-pyran (formula II.1; 1.24mol), 141 ml of water and 83.7 g of acetone (1.44 mol) were mixed with11 g of 50% by weight of sulfuric acid and were refluxed for 3 hours.The pH was 0.9.

Thereafter, the condenser was replaced by a distillation bridge andaqueous acetone was distilled off over a period of 3 hours at 70-80° C.and 1 bar.

The mixture was allowed to cool to room temperature and a pH of 5.2 wasestablished with 25% by weight of aqueous sodium hydroxide solution.Further volatile components were then distilled off at 55° C. and 450mbar. 297 g of adduct 1.3 were obtained in the form of an amber-coloredoily product having a broad molar mass distribution (Q=5.2) with anM_(n) of 810 g.

1.4. Preparation of Adduct 1.4

In a 1 liter three-necked flask having a condenser, stirrer andthermometer, 141 g of 2-methoxy-2,3-dihydro-4H-pyran (formula II.1; 1.24mol), 141 ml of water and 83.7 g of acetone (1.44 mol) were mixed with70% by weight of methanesulfonic acid and were refluxed for 3 hours. ThepH was 0.9.

Thereafter, the condenser was replaced by a distillation bridge andaqueous acetone was distilled off at 82° C. and atmospheric pressurevolatile components over a period of 3 hours.

The mixture was allowed to cool to room temperature and a pH of 5.3 wasestablished with 6 ml of 50% by weight aqueous sodium hydroxidesolution. Further volatile components were then distilled off at 55° C.and 550 mbar over a period of one hour. 280 g of adduct 1.4 wereobtained in the form of a yellow oily liquid having a broad molar massdistribution (Q=3.8) with an M_(n) of 840 g.

1.5. Preparation of Adduct 1.5

In a 1 liter three-necked flask having a condenser, stirrer andthermometer, 141 g of 2-methoxy-2,3-dihydro-4H-pyran (formula II.1; 1.24mol), 144.3 g of aqueous formalin solution (1.44 mol of formaldehyde)and 45 ml of water were mixed with 7.5 g of a 70% by weightmethanesulfonic acid and were refluxed for 3 hours. The pH was 0.9. Thecondenser was then replaced by a distillation bridge and aqueous acetonewas distilled off at 75° C. and atmospheric pressure over a period of 3hours.

The mixture was allowed to cool to room temperature and a pH of 4.2 wasestablished with about 9 ml of 50% by weight aqueous sodium hydroxidesolution. Further volatile components were then distilled off at 49° C.and 35 mbar. 151 g of adduct 1.5 were obtained in the form of an oilybrown product having a broad molar mass distribution (Q=4.6) with anM_(n) of 1 120 g.

2. Tanning Experiments 2.1. Inventive Tanning Experiment 2.1

Data in % by weight are based on the pickle weight unless statedotherwise. 750 ml of water and 3% by weight, based on the pickled pelt,of the adduct 1.1 were added to strips of pickled cattle pelt having asplit thickness of 2.5 mm and each weighing 2 500 g at a pH of 3.0-3.2and 25° C. in a 10 l barrel. After a drumming time of 60 minutes, 2% byweight of the sulfone tanning agent Basyntan® SW (BASFAktiengesellschaft) were added and drumming was effected for a further 2hours. The pH was then brought to 4.9-5.1 with 0.5% by weight ofmagnesium oxide in the course of 6 hours. The liquor was discharged andthe hide was washed with 300 ml of water. After samming, the hides wereshaved to 1.6-1.8 mm. The inventive semifinished product 2.1 wasobtained.

The shavability was determined by experiments on a shaving machine.Shaving machines operate with rotating blades. In the case of poorshavability, the blades slid over the surface and the temperature on thesurface of the leather increased so that horny fusion irreversiblydamaged the hide. The rating was effected according to a rating systemfrom 1 (very good) to 5 (poor).

2.2 to 2.5. Inventive Tanning Experiments 2.2 to 2.5 and ComparativeExperiment C 2.6

The tanning experiment described above was repeated except that theinventive adduct 1.1 was replaced by the inventive adducts 1.2, 1.3, 1.4and 1.5 respectively.

This correspondingly produced the inventive semifinished products 2.2,2.3, 2.4 and 2.5 respectively.

Comparative experiment C 2.6 was carried out analogously, but theinventive adduct was replaced by 3% by weight of glutaraldehyde (50% byweight aqueous solution). The comparative semifinished product C 2.6 wasobtained.

The shrinkage temperatures were determined according to the method fromDIN 53 336 (year 1977), the method having been modified as follows:

-   -   Point 4.1: The samples have the dimensions 3 cm·1 cm; the        thickness was not determined.    -   Point 4.2: Only one specimen per leather sample was tested        instead of 2.    -   Point 6: Omitted    -   Point 7: The drying in the vacuum desiccator was omitted.    -   Point 8: The shrinkage temperature was measured when the pointer        returned.

The rating of the shavability and of the yellowing were effected on thefollowing rating scale: 1 very good, 2 good, 3 satisfactory, 4 adequate.TABLE 1 Result of the tanning and analytical evaluation of inventivesemifinished products Shrinkage Semifinished temperature Number productShavability [° C.] Yellowing 2.1 2.1 3 74.5 2 2.2 2.2 2.5 76 2.5 2.3 2.32 77.5 2.5 2.4 2.4 2 79 2 2.5 2.5 3 74 3.5 C 2.6 Glutaraldehyde 3 77 4

3. Production of Inventive Leathers and Comparative Experiment

Data in % by weight are based on the shaved weight, unless statedotherwise.

3.1. Production of Leather 3.1 from Semifinished Product 2.1

1 800 g of semifinished product 2.1 was drummed together with thefollowing agents for 20 minutes:

120% by weight of water, 5% by weight of the sulfone tanning agentBasyntan® SW (BASF Aktiengesellschaft) and

4% of a 30% by weight aqueous solution of a methacrylic acid homopolymerpartially neutralized with NaOH and having the following analyticaldata: M_(n) about 10 000; Fikentscher K value: 12 (determined as 1% byweight aqueous solution), viscosity of the 30% by weight solution: 65mPa·s (DIN EN ISO 3219, 23° C.), pH 5.1.

6% by weight of the vegetable tanning agent Tara® (BASFAktiengesellschaft) and 2% by weight of the resin tanning agent Relugan®S (BASF Aktiengesellschaft) and 2% by weight of the dye Luganil® brownNGB were then metered and the mixture was drummed. After two hours, a pHof 3.6 was established with formic acid. 6% by weight of LipodermliquerCMG® (BASF Aktiengesellschaft) and 1% by weight of Lipamin OK® (BASFAktiengesellschaft) were added as a fatliquoring component. After adrumming time of a further 60 minutes, the pH of 3.2 was establishedwith formic acid. Before the liquor was discharged, a sample of theliquor was taken. The liquor was discharged.

The leather thus obtained was washed twice with 100% by weight of watereach time, stored moist overnight, partly dried on a toggle frame at 50°C. and then dried. Leather 3.1 was obtained. After staking, leather 3.1was assessed as below.

The evaluation was effected according to a rating system from 1 (verygood) to 5 (poor). The evaluation of the liquor exhaustion was effectedvisually according to the criteria of residual dye (extinction) andturbidity (fatliquoring agent), from which the mean value wascalculated.

EXAMPLES 3.2 TO 3.5, COMPARATIVE EXAMPLE C 3.6

The above example was repeated, but in each case with inventivesemifinished product 2.2 to 2.5. For comparative example C 3.6, thesemifinished product from comparative example C 2.6 was furtherprocessed. The evaluation of the performance characteristics is shown intable 2. TABLE 2 Liquor Grain Tensile Stitch tear Leather exhaustionBody tightness Softness strength [N] resistance Levelness 3.1 3 2.5 33.5 256 196 2.5 3.2 2.5 2.5 2 3 270 194 2.5 3.3 2 1.5 2.5 2 283 201 13.4 1.5 1 1.5 2 287 229 1 3.5 1.5 2.5 2 2.5 260 218 1.5 C 3.6 3 3.5 3.53 247 191 3

The tensile strength was determined according to DIN 53328.

The stitch tear resistance was determined according to DIN 53331.

1. An adduct obtainable by reacting carbonyl compounds of the formula I

where R¹ and R² are selected from hydrogen, C₁-C₁₂-alkyl, C₃-C₁₂-cycloalkyl, substituted or unsubstituted, C₇-C₁₃-aralkyl, C₆-C₁₄-aryl, substituted or unsubstituted, it being possible for R¹ and R² to be linked to one another with formation of a ring, with cyclic compounds of the formula II

where X is selected from the group consisting of oxygen, sulfur and N—R⁸, R³ and R⁸ are identical or different and are selected from hydrogen, C₁-C₁₂-alkyl, C₃-C₁₂-cycloalkyl, substituted or unsubstituted, C₇-C₁₃-aralkyl, C₆-C₁₄-aryl, substituted or unsubstituted, formyl, CO—C₁-C₁₂-alkyl, CO—C₃-C₁₂-cycloalkyl, substituted or unsubstituted, CO—C₇-C₁₃-aralkyl, CO—C₆-C₁₄-aryl, where X is N—R⁸, it being possible for R³ and R⁸ to be linked to one another with formation of a ring; R⁴, R⁵ and R⁶ are identical or different and are selected from the group consisting of hydrogen, C₁-C₁₂-alkyl, C₃-C₁₂-cycloalkyl, substituted or unsubstituted, C₇-C₁₃aralkyl, C₆-C₁₄-aryl, substituted or unsubstituted, it being possible in each case for two neighboring radicals to be linked to one another with formation of a ring; n is an integer in the range from 1 to 4; R⁷ are identical or different and are selected from hydrogen, C₁-C₁₂-alkyl, C₃-C₁₂-cycloalkyl, substituted or unsubstituted, C₇-C₁₃-aralkyl, C₆-C₁₄-aryl, substituted or unsubstituted, it being possible for R⁷ to be linked to R⁶ or in each case two neighboring radicals R⁷ to be linked to one another with formation of a ring.
 2. The adduct as claimed in claim 1, wherein X is oxygen.
 3. The adduct as claimed in claim 1, wherein R⁴ to R⁷ are each hydrogen.
 4. A mixture comprising at least one adduct as claimed in claim 1 with byproducts arising from the preparation or storage thereof.
 5. A process for the preparation of an adduct as claimed in claim 1 or a mixture as claimed in claim 4, wherein carbonyl compounds of the formula I are reacted with cyclic compounds of the formula II.
 6. The process as claimed in claim 5, wherein the reaction is carried out at acidic pH.
 7. (canceled)
 8. A process for the production of semifinished products and leather, wherein an adduct as claimed in claim 1 or a mixture as claimed in claim 4 is used.
 9. The process as claimed in claim 8, wherein an adduct as claimed in claim 1 or a mixture as claimed in claim 4 is used in a form diluted with a polar solvent.
 10. The process as claimed in claim 9, wherein one or more adducts as claimed in claim 1 or mixtures as claimed in claim 4 are used as an active ingredient in powder form.
 11. An active ingredient in powder form, comprising from 10 to 100% by weight of one or more adducts as claimed in claim 1 or a mixture as claimed in claim 4 and from 0 to 90% by weight of one or more additives.
 12. The active ingredient in powder form as claimed in claim 11, in which the additive or additives is or are selected from the group consisting of starch, silica, sheet silicates, alumina and mixed oxides of silicon and aluminum.
 13. A process for the preparation of an active ingredient in powder form as claimed in claim 11, wherein said active ingredient is obtained by spray-drying.
 14. A process as claimed in claim 8, wherein one or more adducts as claimed in claim 1 or mixtures as claimed in claim 4 are used in a form diluted with a polar solvent, in the presence of additives.
 15. A semifinished product or a leather, produced by a process as claimed in claim
 8. 16. The adduct as claimed in claim 1 or the mixture as claimed in claim 4, wherein the adduct or mixture is a preservative.
 17. The active ingredient in powder form as claimed in claim 11, wherein the active ingredient is a preservative. 